1. of or relating to the sun; solar
Usage: technical; astronomy
2. relating to the heliacal rising or setting of a star (its first or last visibility in relation to the sun)
Usage: astronomy; technical

Examples

• The heliac rising of Sirius was an important event in the ancient Egyptian calendar.
• Astronomers track the heliac phenomena of bright stars to understand their orbital positions.
• The heliac setting of a star marks its disappearance into the sun's glare.
• Ancient civilizations used heliac observations to predict seasonal changes.